


Coming of Age

by doitsushine92



Category: EXO (Band)
Genre: Alpha!baekhyun, Alpha/Beta/Omega Dynamics, Alpha/Omega, Alternate Universe - High School, Friendship, Knotting, M/M, Smut, omega!sehun
Language: English
Status: Completed
Published: 2017-02-04
Updated: 2017-02-04
Packaged: 2018-09-22 00:16:48
Rating: Explicit
Warnings: Underage
Chapters: 1
Words: 4,141
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/9573191
Author URL: https://archiveofourown.org/users/doitsushine92/pseuds/doitsushine92
Summary: Sehun had been avoiding Baekhyun for a week. But just as Baekhyun is about to give him an earful, Sehun goes into heat for the first time.





	

**Author's Note:**

> crossposted from aff
> 
> i wrote this for I because she's whiny and wanted sehun smut

Sehun was 7 years old when they met. It was the first day of school, and Sehun kept bouncing up and down impatiently, small hands tugging at his backpack’s straps as he waited for his hyung to be ready. It was a sunny day, not a cloud in the sky and Sehun could feel his wolf howl with excitement. He was tempted to ditch his brother and go for a run in the woods casually placed behind his house, but he also really wanted to go to school, so he settled for running up the stairs and barrelling into his brother’s room to see what was taking him so long.

Seho was 10 years old, and was already entering 4th grade, while Sehun was barely starting 1st grade. So it came as no surprise when his brother pushed Sehun out almost immediately, saying something about squirts and privacy that Sehun didn’t really understand but complied with Sehun’s whims and walked out with him, messenger bag slung over his shoulder. They yelled goodbye to their parents and then raced each other to the bus stop a block away.

Sehun won, as usual, and Seho ruffled his hair when he caught up, winded and face flushed. Sehun was smiling so hard he felt like his face was going to split into two and his brother even gave him some advice on school. Sehun realized that it had been the longest they had spent together without arguing. But then Seho’s friends showed up and Sehun was left to sit on the bench by himself and making small talk with Jinri, whose older sister had been attending school with Seho for years. Jinri was actually starting the 2nd grade, having been promoted a year because she was smarter than the kids in her class, but promised Sehun they would play together during recess, and Sehun was glad to know there would be a familiar face around.

His day went uneventful, his giddiness slowly melting away as time went by. Recess time rolled around and Sehun found himself being dragged into the playground by Jinri and two other kids that Sehun found out were named Jongin and Soojung. They played around for a long time, until Soojung suggested they played Hide and Seek. Jongin was it, and the moment he started counting, they all dashed in different directions. Sehun darted for a secluded corner he had noticed between the swing sets and the building; it was poorly illuminated and, from what Sehun had seen, Jongin wasn’t the most observant, so he probably wouldn’t be found too soon. 

He was crouching down; hand covering his mouth to muffle his giggles when a shadow fell over him and Sehun looked up to see an older boy giving him an intimidating look. Sehun gulped.

“Are you the kid that’s been hanging around Jinri?” the boy asked, and his voice sounded menacing in Sehun’s ears. He nodded, not knowing really well what to do, and his heart nearly stopped when the kid threw his head back and shouted, “I found him!”  
Five more kids walked into his hiding spot, and the taller, meaner looking one bent down to look at him. Then, without saying anything, pushed Sehun so he landed on his ass. It didn’t exactly hurt him, but Sehun had always been more sensitive, so it wasn’t too surprising when his eyes filled with tears. The other kids laughed while the culprit slammed his small feet against Sehun’s torso and this time the tears rolled down his cheeks. Sehun curled into a ball, expecting another hit, but the sound of a fight reached his ears and he peeked out from under his arm to see another boy scaring his bullies away. When the mystery boy had successfully driven them out of the alley, he started moving towards Sehun and he cowered again, afraid he would be next. He did not expect warm hands tugging him up, shifting him around so he was facing the other kid. The boy looked older than him, but younger than Seho, with curly brown hair, large puppy eyes and a cute button nose.

“Hey, are you ok?” the boy asked, soft finger brushing through his hair, “Don’t cry, I told them to go away so they won’t bother you anymore. I’m Baekhyun, by the way!”

Sehun sniffed, subconsciously leaning into the touch, “My name is Sehun… and thank you,” he added in a small voice, eyes casted down.

Baekhyun had smiled, and Sehun was miffed for a moment because the older boy had really nice teeth. For a kid, anyway. They were slightly crooked, but they seemed to shine like stars. He never really found out what those kids wanted with Jinri, but he figured one of them had a crush on her. He wouldn’t have been surprised.

After that day, Sehun attached himself to Baekhyun, not that the older boy cared. He continued playing with Jinri, and Jongin became one of his best friends, and Soojung was also really cool to hang out with, but Sehun felt infinitely safer and warmer with Baekhyun.   
-  
Years later, when Baekhyun turned sixteen and his status as Alpha was confirmed, Sehun found he wasn’t surprised at all. Despite the height difference, Baekhyun had always been more dominant in a way, and people usually noticed him first. There was something in the way he walked, how he spoke and his stance that seemed to call for attention. Before his coming-of-age, people used to make fun of him for his stature, but Sehun knew that underneath the soft exterior hid muscles and strength. He was lively, playful and sociable, with boisterous laughter and loud personality, but he was also a leader, people followed him and his every command.

Sehun, on the other hand, was the shy one. He tried hiding under large hoodies and behind Baekhyun, not that it worked. He was so tall; people could see him at the other end of the room, while Baekhyun was smaller and cuter. So he took to hiding behind Jongin instead. Baekhyun was always trying to coerce him into going to parties with him, to hang out with other people, but Sehun always said that just having their small group was enough. So whenever Baekhyun, Jongin and Soojung went out to party with their school friends, Sehun chose to stay at home with Jinri, furrowed under blankets and bickering over what Disney movie to watch.

That was practically every Friday, with Saturdays spent babysitting Baekhyun and Jongin through their hangovers, because Jinri could barely handle Soojung on her own. And then Sunday came along and Sehun would realize how much homework he had neglected and, after cursing those two monsters out over the phone, he’d pull an all-nighter in a poor attempt to salvage his grades.

It had become a tradition and, much to his despair, he liked it.   
-  
Before Sehun’s 16th birthday, his parents took him out for dinner. Seho had stayed behind, excusing himself with college essays, despite everyone (see: Sehun) knowing that the real reason was that his parents were going to talk to him about his probable status as an omega and his brother really didn’t want to be there. 

The dinner turned out to be getting pizza and sitting out in the backyard of their home. Sehun preferred it that way, because he hated being in public. His mom and dad made casual talk with him, asking him for his friends and school. Inevitably, the subject turned to Baekhyun, because Sehun was unable to go five minutes without bringing him up. 

“It’s Baekhyun’s last year, right?” his father asked, wiping the corner of his mouth with a napkin, “How’s he doing?”

“You know him,” Sehun answered, “He likes to pretend like everything is ok, even though I know he’s freaking out on the inside.”  
His mom started cleaning up, stacking plates and crumbled napkins on top of the pizza boxes, a habit she had whenever she got nervous, and Sehun noticed. 

“Listen, son,” his father continued, “We wanted to talk to you about something. We know you and Baekhyun are really close and he’s leaving, so we wanted to make sure you were ok, too.”

His mother continued, “Your birthday is next week, and I know nothing is set in stone, but -”

“You think I’m an omega,” Sehun interrupted, matter-of-factly, “I know, I think so too.” There was nothing to hide; Sehun knew perfectly well that the odds of him being an omega were pretty high. Every rank had almost specific personality traits, and Sehun shared them with the omegas around him.

“Right, that’s why maybe, when Baekhyun leaves for college, you might feel a little lost,” his mother was at it again, her hands itching to find something to fix. 

It dawned on him that Baekhyun was leaving for college. He knew his best friend was graduating, but he hadn’t realized that his university of choice was all the way across Seoul. That night, Sehun got little to no sleep, thinking of how the hell he was supposed to make it through two years without Baekhyun.

Sehun tried his hardest to pretend like everything was ok, leaning into Jongin (Alpha) during every class they had together and letting Soojung lean into him the rest of the time. Jinri (Beta) had been stressing out over finals, so Sehun took to staying with her during lunch breaks to calm her down during her melt downs. 

He was not so stealthily avoiding Baekhyun, and he knew the elder knew, but he was still freaking out, so it was probably better. He knew Baekhyun wouldn’t take it for long and would eventually confront him, but he chose to ignore that thought. 

Leave it to Baekhyun, though, to wait until Sehun’s birthday to corner him. It was nearing the end of the day and Sehun had a free period. Jongin was coddling him in the bleachers, and Sehun revelled in the attention. Jongin had bought him an extra slice of cake at lunch and was spoon feeding him when Baekhyun approached. Sehun tensed.

“Hey hyung,” Jongin greeted him cheerfully; “I thought you had Calculus?”

“I sneaked out,” Baekhyun said honestly, shrugging his shoulders, “Told Mr. Park I had a stomach ache, because I figured I should come and hang out with Sehunnie because, otherwise, I won’t see him at all.” Baekhyun said it almost nonchalantly, picking at his nails, but there was an undertone, like he was pissed and Jongin noticed, because he curled his hand around Sehun’s wrist protectively. Sehun appreciated the touch, the support, and he leaned his head into Jongin’s shoulder. He pretended not to notice how Baekhyun’s nostrils flared at the action.

They talked, though the conversation was awkward and strained. When the final bell rang, Baekhyun stood up and, with a quick “See you later, Jongin,” he tugged Sehun towards his car. The parking lot was behind the field so it wasn’t a long walk, though that didn’t stop Sehun from trying to squirm free of the elder’s grip; the kid had dainty fingers, but they were strong and most likely going to leave a mark. The car ride was silent, and the only moment he chanced a peek at Baekhyun, he noticed the elder’s hands were gripping the steering wheel so hard his knuckles were white. Sehun chose not to mention that both their backpacks had been left behind at school; Jongin could take care of those. 

Baekhyun parked the car in his driveway, and Sehun gulped when he realized that his parents weren’t home, and Baekbeom was in college, so no one would be there to save him. Baekhyun nearly pushed Sehun inside, door slamming shut behind them. Sehun hadn’t taken three steps into the living room when there was a hand spinning him around, and his back met the wall. 

Baekhyun seemed to hover over him, and Sehun knew, at the back of his mind, that Baekhyun was exerting his dominance.   
Sehun gulped; Baekhyun had never pulled that on him. His hyung’s eyes were angry, and Sehun nearly whimpered when Baekhyun wedged a knee between Sehun’s legs, successfully lifting his feet off the ground, and Sehun registered that as his way of controlling him. There was sinking feeling in his stomach.

“May I ask why the fuck you’ve been avoiding me?” Baekhyun asked, eerily calm. His breath hit Sehun’s face in hot puffs. Sehun remained silent, and Baekhyun didn’t like that all, because suddenly his left hand was tugging Sehun’s hair, hard.

“Well?” he demanded, roughly, and Sehun whimpered. 

“I-I,” Sehun struggled to answer, but there was an unfamiliar sensation coiling in his stomach and it was very distracting. He felt lightheaded, and Baekhyun seemed to notice too, because he lowered his knee and his hand left Sehun’s hair to grab his chin.

“Look at me,” he said, eyes searching his face until his pupils dilated and Sehun got a sense of dread, “Sehunnie, I think you’re going into heat.”

Sehun nearly moaned out loud at the sound of Baekhyun’s voice, which had gone gravely and dropped an octave lower. His fingers scrambled to find purchase, settling for holding onto Baekhyun’s arms and the elder cursed. Sehun faintly noticed he was starting to sweat and all the blood in his body was travelling south.

“Do you want me to call your parents?” Baekhyun asked, and that was probably a good idea, but Sehun was getting dizzy with warmth and Baekhyun smelled delicious.

“No,” he croaked out, head shaking frantically, “Hyung, I’m… I’m so hot, please help me.” 

The heat was getting unbearable and his hyung was so soft, Sehun nearly tripped over himself when Baekhyun guided him to the couch. Sehun almost cried when Baekhyun took his hands off his body, but luckily he seemed to understand the whine that escaped Sehun’s throat, because he was immediately holding one of his hands while the other pushed away wet strands of hair from his face.

“Sehunnie,” he started warily, “You’re not thinking coherently.” Baekhyun’s voice sounded strained. 

Sehun did cry this time, a single tear escaping him at the same time his hands started pulling his shirt off. He heard Baekhyun’s sharp intake of breath, but didn’t pay any attention to him because the cool air felt amazing on his cool skin, nipples pink and pert.

However, as Sehun was about to take his pants off to free his erection, which was painful and all sorts of uncomfortable, Baekhyun stopped him. Sehun didn’t know whether to snap at him or cry.

“Sehun,” his hyung sounded so good, “Do you know what’s going on? Do you understand that if you carry on with this, I won’t be able to stop myself?”

That sounded pretty good to Sehun. He whined, canting his hips up and Baekhyun seemed to make a split decision then and there, because his nimble fingers were unbuckling his belt and helping him take his jeans off. Sehun was so glad it was Casual Friday, because his school uniform was impossible to take off. 

“It’ ok, Sehun,” Baekhyun reassured him, “I got you.”

Once Sehun was stripped down to his boxers, shoes and socks kicked off in the process, Baekhyun took him in his arms and carried him upstairs, kicking his door open and then kicking it back closed, laying Sehun down in the middle of his bed carefully. Sehun was suddenly overwhelmed with the scent of alpha, of Baekhyun, and he whimpered. Baekhyun unbuttoned his own dress shirt, his eyes never leaving Sehun’s, and casted it aside, his own pants following. There was a moment of hesitation, in which Sehun trailed his eyes down Baekhyun’s body, noticing what great hips his hyung had, before Baekhyun was on top of Sehun, their lips crashing together almost painfully.

It wasn’t their first kiss together, considering the awful friends they had and their love for Truth and Dare, but it was definitely the first time it was so intense. Baekhyun forced his tongue inside Sehun’s mouth right away, making Sehun arch his back and the kiss became open mouthed, spit trailing down their chins. The room was getting hotter as time progressed, and Sehun was sweating even more now. Baekhyun separated in favour of trailing his mouth down Sehun’s neck, sucking and pulling at various patches of skin, Sehun moaning in the process. 

He nearly passed out when one of Baekhyun’s hands cupped his boner through his boxers, circling in a slow motion and the sound that left Sehun’s mouth could not have been made by him. He felt Baekhyun smirk against his neck and Sehun had half a mind to smack him over the head, but his arms were too weak to lift them.

“Hyung,” he rasped out, and Baekhyun hummed in acknowledgment, “I feel… funny,” Sehun rubbed his legs together uncomfortably; there was a weird sensation between his ass cheeks.

“Maybe its self-lubrication,” Baekhyun suggested, mouth no longer on his neck, but now he was straddling Sehun, one hand still massaging his cock while the other flicked at his nipples. There was a teasing smirk on his face, and Sehun was growing more tempted to hit him as time went by. Sehun blushed at the thought of being wet for Baekhyun; being in heat made you hot all over and horny, but you needed to be truly needy and ready to mate to produce slick. Baekhyun looked at him considerably, like he was trying to decide what to do with him next, and Sehun squirmed underneath him. Finally, his hyung pulled his boxers down, his hard cock slapping against his stomach.

“Yup, definitely self-lubrication,” Baekhyun sounded so smug. Sehun hated him. There were hands on his knees, pushing them apart with care, and Sehun had never felt more exposed. He must be quite the sight; flushed, panting, cock an angry red and wet. “Fuck, Sehun, you’re leaking.” Baekhyun was now more impressed than smug. Baekhyun trailed a finger up his crack, collecting some of his wetness while Sehun groaned and then popped the finger in his mouth, tasting Sehun.

“You taste really good,” he hummed as he collected some more and this time; he pressed a finger inside his hole. Sehun gasped, not used to the feeling. It was odd; not bad, but odd. His hyung’s fingers curled upwards, scratching against his walls and Sehun could have died right then and there.

Baekhyun thrusted his finger in and out carefully, until he had made sure Sehun was stretched and then pushed another one in and Sehun hissed in pain. It took longer for Sehun to adjust, but Baekhyun rubbed his thigh with his free hand soothingly. After a minute, Sehun started rolling his hips down, trying to get Baekhyun to move and his hyung didn’t waste any time, scissoring and stretching his hole open. Sehun’s eyes rolled to the back of his head when he felt a hot tongue sliding alongside his fingers. He felt Baekhyun moan against his rim at the taste and the vibrations sent chills up Sehun’s spine.

When the third finger was in, Sehun was moaning endlessly, his hips rolling down to meet with his hyung’s movements. Baekhyun pulled away and Sehun whimpered at the sight of the elder’s face coated in his slick. Instead of wiping his face, Baekhyun surged forward to connect his lips with Sehun’s and let him have a taste of himself. Sehun whined at the loss of fingers, but then Baekhyun was stripping off his boxers and Sehun almost choked at the sight of the alpha’s cock, all swollen and the tip was almost purple. 

Baekhyun pulled Sehun’s legs up and placed them over his shoulder, settling between his thighs while his other hand pumped leisurely at his own dick. Sehun watched as Baekhyun licked over his bottom lip, pink tongue testing his sanity and he whined as his hyung’s eyes travelled all over his body. Sehun returned the action, taking Baekhyun’s body, his thighs, waist, and hips.   
“Are you sure you want to do this?” Baekhyun asked, uncertainty taking over his features. Sehun whined at him, “Yes, so could you please, just…” he trailed off.

Baekhyun got the stupidest smirk on his face and said, “Please, what? Sehunnie, I can’t do anything if you don’t tell me what you want.”

Sehun felt his face flaming, and then it got worse; “Come on, Sehun, tell hyung what you need,” Baekhyun cooed.

“I... I need-” Sehun whimpered, “I need your…” 

“Yeah, baby?”

Sehun blushed even more at the pet name. “I need your cock,” he mumbled at last, “Please knot me.”

Baekhyun’s smirk was sickening and uncalled for. Sehun wanted to die. But then his hyung was pushing into him, and Sehun felt like he was going to die. It stretched his muscles so far, more than what he had been prepared for, and Sehun gripped the sheets beneath him in an attempt to ground himself. Baekhyun rubbed soothing circles on his stomach, telling him what a good boy he was. 

“Fuck, Sehun, so tight,” he groaned, hips hitting Sehun’s thighs as he slid in all the way, “You’re taking my cock so well, you’re so good.” He caressed his cheek in a sudden show of affection, Sehun leaning into the touch. 

Sehun laid still after that as he adjusted to having Baekhyun’s dick in him. He didn’t notice he had his eyes closed until then, but when he reopened them he nearly blew his load at the sight of Baekhyun, the veins in his neck straining as he forced himself to stay grounded for Sehun’s sake, eyes almost black and shoulders tensed and the omega felt something thudding in his heart.

“Hyung, I… you can move now,” Sehun whispered. Baekhyun looked down at him, and there was a strange look on his eyes, but Sehun didn’t have much time to process it because then Baekhyun was pulling out, slowly, and then pushing back in.

His pace was gentle at first, although it was more to tease Sehun than anything, letting him feel the drag of his cock against his walls. Baekhyun groaned above him, Sehun’s ass sucking him in and it felt unbelievably good. 

Baekhyun pulled out slowly one last time, relishing in how Sehun’s hole clenched around the tip of his cock, and right before he was all the way out, he leaned forward and rammed his hips down. Sehun let out the loudest moan of the night, hands clawing at Baekhyun’s back. Sehun cried out when he felt the tip of Baekhyun’s dick bump against his prostate, and the elder angled his hips to hit that spot over and over. 

There was only the sound of skin slapping against skin, Sehun’s whimpers bouncing off the walls and Baekhyun’s occasional groans. The alpha’s cock began to swell and soon it was too big to pull out, stretching Sehun impossibly wide. Baekhyun opted for grinding his hips down then, looking blissed out and Sehun’s gut twisted pleasantly.

“Sehun, I’m-” Baekhyun groaned, hips stuttering. Sehun whined in response, his left hand going to rub at his cock before it was slapped away by Baekhyun, and then his hyung’s pretty fingers were stroking him to completion. Sehun moaned long and loud, his cum coating Baekhyun’s fingers and his own chest, and the contraction of his ass muscles tipped Baekhyun over the edge. His hyung growled into his ear as he cummed, and Sehun whined at the oversensitivity as Baekhyun continued moving as he rode out his orgasm, filling Sehun with his cum.

Baekhyun collapsed on top of Sehun, breaths coming out in puffs as he rearranged them to lie comfortably while his knot shrunk. They ended up with Baekhyun on his back as Sehun straddled him, and the movements caused both his knot and his cum to make Sehun whimper.

“Hey,” Baekhyun whispered, “How are you feeling?” 

There were cool fingers on his spine and Sehun sighed. He could feel a smile forming on his lips and he bit it down. But, of course, Baekhyun pulled his chin up and Sehun was met with a dazzling smile that only Baekhyun could come up with.

“I’m fine,” Sehun mumbled. His cheeks were warm. Baekhyun chuckled low on his throat and Sehun found that more attractive than he should have. Sehun was almost asleep when Baekhyun shook his shoulder.

“Yah, you never answered me,” he could hear the pout on his hyung’s face, “Why were you avoiding me?”

“Because you’re leaving soon and I didn’t know what to do,” Sehun mumbled, face hidden in the crook of Baekhyun’s neck.

“That is so stupid,” Baekhyun laughed, “There’s nothing to do except talk to me on the phone and come visit me at least once a month. Oh, and bringing me your mom’s homemade pie, that shit is delicious.”


End file.
